Key locking circuit for a keyboard operated machine



July s, 1969l KEY LOCKING CIRCUIT FOR A KEYBOARD OPERATED MACHINE Filed June 22, 1967 G. scHREM 3,454,147

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ArwuMM July 8, 1969 G, SCHREM 3,454,147

KEY Locxme cIRcuxT Eon A KEYBOARD OPERATED MACHINE File June 22, 1967 sheet of 2 ,47KSI 0 Volf Fig.4

07 234 56789 ivvlvlvlv `INVENTOR WMV (MM United States Patent O U.S. Cl. 197-98 2 Clams ABSTRACT OF THE DISCLOSURE An electronic interlocking circuit for the keys of a keyboard operated machine where the switching of the keys to their normal and to their actuated positions produce output signals alternately actuating a flip-flop circuit. The flip-flop circuit Will respond only to an output signal from an actuated key only after a previously actuated key has returned to its normal position.

The present invention relates to an electronic interlock arrangement for the keys of a keyboard operated machine, more particularly, to an interlock which will transmit the signal generated by a second actuated key only after the first actuated key has been returned to its normal position.

In the generation of signals from the keyboard of a machine, it is known that the keys can be actuated by the operator so rapidly that there is an almost negligible elapse of time between successive actuations. The structures or circuitry involved in the machine require some separation in time in order to respond properly to each actuation of a key. Should there fail to be a minimum separation in time between successive actuations of the key, the machine may malfunction and the keyed data may be lost.

In order to prevent a too rapid Succession of actuated keys, various forms of mechanical and electrical interlocks have been provided. Such interlocks operate in a variety of ways to prevent the machine from receiving an uncontrolled mixture of electrical impulses when two keys are depressed simultaneously. Such devices usually operate by blocking the signal from the second key until after the first actuated key is released to its normal position.

The mechanical interlocks may take many forms but generally operate on the concept of wedge or ball displacement. Such mechanical interlocks are generally satisfactory in operation except that they are noisy and slow and, accordingly, significantly decrease the efliciency and productivity of the machine.

It is therefore the principal object of the present invention to provide a novel and improved electronic interlock for the keys of a keyboard operated machine.

It is a further object of the present invention to provide an electronic key interlock for various electrical machines such as calculators which is considerably quicker and less noisy in operation than similar devices.

According to the present invention an electronic circuit is provided wherein a signal generated by an actuated key is not passed to the calculator until the key generating a preceeding signal has been returned to its normal or resting position. Thus, where a Succession of generated signals are superimposed upon each other, the signals will be transmitted in Succession to the calculator only upon the return of the preceeding actuated key to its normal position.

In one aspect of the present invention there may be 3,454,147 Patented July 8, 1969 provided a machine operated by a keyboard and having a number of manually actuated keys with each key having a normal and an actuated position. A first switching circuit is connected to the normal contacts of the keys to generate an output signal When the keys are in their normal position. A second switching circuit is connected to the actuated contacts of the keys to generate an output signal upon the actuation of a key. A flip-flop circuit having two inputs has one input connected to the first switching circuit and the second input to the second switching circuit. The flip-flop circuit is actuated by an output signal from the second switching circuit. The flip-flop circuit returns to its nonconductive state when the actuated key is released and returned to its normal position. A storage register means is connected to the second switching circuit to store a second output signal generated by switching a second key from its normal to its actuated position when a previously switched key has not as yet returned to its normal position. This second output signal is transmitted to the flip-flop circuit from the Storage register means after the first key has returned to its normal position.

Other objects and advantages of the present invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings wherein;

FIGURE 1 is an electrical circuit diagram showing schematically the various components of the electronic interlock circuit according to the present invention;

FIGURE 2 is an electrical circuit diagram showing schematically but in greater detail switching circuit A of FIGURE 1;

FIGURE 3 is an electrical circuit diagram showing schematically but in greater detail switching circuit B of FIGURE 1; and

FIGURE 4 is an electrical circuit diagram of the storage register of FIGURE 1.

Proceeding next to the drawings wherein like reference symbols indicate the same parts throughout the various views a specific embodiment of the present invention will be described in detail.

As may be seen in FIGURE 1, the present invention is incorporated in an electrical calculator having a number of manually depressible digital keys 10 carried in a keyboard. Each key is positionable between a normal contact 11 and an actuated contact 12. The keys are of the type which tend to return to the normal position as illustrated in FIGURE 1. The normal contacts 11 are connected through leads 13 to a switching circuit A which is illustrated in greater detail in FIGURE 2 and the actuated contacts are connected to a switching circuit B illustrated in FIGURE 3.

As may be seen in FIGURE 2, each normal contact 11 is connected to a common output line 14 through a capacitor 15 and a diode 16. In addition, resistors 17 and 18 are connected between a minus 24 vo'lt line and lead 13 on either side of capacitor 15. A pair of resistors 19 and 20 are also connected to the output line 14, as shown in FIGURE 2. The output 14 is connected to the input of an amplifier C which has an output 21 connected to one input of a fli-p-flop circuit D.

As may vbe seen in FIGURE 3, each actuated contact 12 is connected through a diode 22 to a common output line 23 which is connected to a second input of the flipfiop circuit D.

In addition, each actuated contact 12 is connected through a lead 24 to a Storage register indicated generally at 25 in FIGURE 1 and illustrated in detail in FIGURE 4. As shown in FIGURE 4 a register is provided for storing each individual digit with these registers being indicated at 26. The stored values are released from their respective registers in response to a key signal collected at F. The key signal is formed in a switching circuit E which is illustrated in FIGURE 1, is connected to the output of flip-flop circuit D. The output of switching circuit E is then connected to the calculator and transmits the value to the circuitry or other structure to operate the machine.

The switching circuit E forms the key or Command signal which actuates the Storage register to transmit the digital values in the sequence in which they are actuated by their respective keys. Further, this command signal operates after an actuated key has been returned to its normal position. The Command signal is formed in circuit E after a momentary delay of about 5-10 ms. and after the impulse from the actuated key has passed through. After this impulse signal has been transmitted to the calculator, the Command signal then actuates the Storage register to transmit the next actuated Signal to th flip-flop circuit.

In the operation of the electronic interlock according to the present invention, a combined output signal is generated in switching circuit A when the keys are in their normal position. At point X in circuit A as shown in FIGURE 2, there will be zero voltage while the key for the digit zero is in the normal position but a voltage of minus 24 when this key actuated. This fluctuation in Voltage is transmitted by capacitor from point X to point Y where the resulting Voltage impulse will be negative When the key is opened or actuated and positive when the key is closed to its normal position. At point Z in circuit A there will be a voltage of about minus 18 volts. When a more positive Voltage is formed at one of the points Y by -the actuation of respective key, this voltage wil'l be transmitted by one of the respective diode 16 to the point Z. At the same time in switching circuit A all of the keys that are in their normal positions will produce a combined signal and in switching circuit B the actuated contacts of the switches of the digital values 0-9 will be combined.

The output Signal from switching circuit A serves to reset flip-flop circuit D or to return the flip-flop circuit to its nonconductive state. The flip-flop circuit D is actuated to its conductive state upon the passage of electric current from switching circuit B to the second input of the flip-flop D. In its actuated condition, the flip-flop circuit D Will transmit only a single impulse in response to the digital value of the actuated key. If a second key is actuated while the first key is being actuated and has not yet retumed to its normal position, the signal from the second key will not be effected. This second signal will be transmitted to the Storage register where it wi-ll remain until the first actuated key has returned to its normal position. At that time the Stored signal from storge register will be transmitted from switching circuit B to the flip-flop circuit which will then be actuated in response to this second signal. The fiip-flop circuit D can be actuated by a signal from circuit B only when the flip-flop circuit has previously been reset by the amplified signal from switching circuit A.

Since switching circuit E will not give a Command signal to switching circuit B and the Storage register connected thereto until an impulse Signal has been transmitted to the calculator, it willbe apparent that only one signal at a time Vis transmitted to the calculator. SuperimpoSed signals resulting from the actuation of the keys in too rapid Succession wil-l be stored in the Storage register and released therefrom in their proper sequence.

Thus it can be seen thatthe present invention provides an electronic key interlock which quickly and elfectively transmits impulse signals to the calculator in the order in which the keys are actuated. The present interlock ar- I rangement has the impoltant advantage in that the jamming of contacts which would result in erroneous signals is eliminated when a second key is actuated in rapid Succession after a first key. Furthermore, the present interlock arrangement is very quiet and rapid in operation because of the electronic components involved.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and, accordingly, it is desired to comprehend Such modifications within the present invention as may fall within the scope of the appended claims.

What is claimed is:

1. In a keyboard operated machine including a plurality of manually actuated keys each being manually operable from a normal position in engagement with a normal contact to an actuated position in engagement with an actuated contact to send an intelligence Signal to a calculator load, the invention which comprises flip-flop means (D) having a pair of input terminals and an output terminal;

means including first switching means (A) and amplifier means (C) for connecting said normal key contacts with one input terminal of said flip-flop means; second switching means (B) for connecting said actuated key contacts with the other input terminal of Said flip-flop means;

third switching means (E) for connecting the output of Said flip-flop means with said calculator load, said second switching means being operable when said flip-flop means is in one condition upon actuation of at least one of said keys to transmit a first intelligence signal to said calculator load via said flip-flop means and said third switching means, said first switching means being operable upon return of said key to the normal position to transmit a reset signal to said flip-flop means via said amplifier means; and

Storage register means (25) connected with said actuated contacts for storing, prior to the return of said one key to its normal position, a second intelligence signal generated by actuation of a second key to its actuated position, said third switching means beingl operable upon transmission of said first intelligence signal to apply a delayed command signal to said Storage register means to effect transmission of the stored second intelligence signal to said flip-flop means.

2. Apparatus as defined in claim 1, wherein Said first switching means includes means for combining the individual signals from the keys in their normal positions to generate Said reset signal.

References Cited UNITED STATES PATENTS 2,7l6,230 8/ 1955 Oliwa 197-107 XR 3,088,401 5/1963 Shimabukuro 101-93 3,091,320 5/1963 Mertn 197-107 XR 3,161,l26 12/1964 Saltz 101-93 3,199,446 8/1965 Schaaf 101-93 3,232,222 2/1966l Jones 101-93 3,234,664 2/ 1966 Yaeger 197-107 XR 3,303,776 2/1967 Rausch 101-93 3,300,758 1/1967 Hawley 340-147 3,308,91S 3/1967 James 197-107 EDGAR S. BURR, Primary Examiner.

U.S. Cl. X.R. 

